An electromechanical power transmission chain comprises typically one or more electrical machines and an electronic power converter. The electromechanical power transmission chain can be a series transmission chain where one of the electrical machines operates as generator and the electronic power converter is arranged to convert the electrical voltages produced by the generator into electrical voltages having amplitudes and frequencies suitable for the one or more other electrical machines. The generator can be driven with a combustion engine that can be e.g. a diesel engine, an Otto-cycle engine, or a turbine engine. The other electrical machines can be, for example, electrical motors in wheels of a mobile working machine. The electronic power converter comprises typically an intermediate circuit, a converter stage between the generator and the intermediate circuit and one or more other converter stages between the intermediate circuit and the other electrical machines. It is also possible that the electromechanical power transmission chain is a parallel transmission chain where the generator is occasionally used as a motor that assists the combustion engine, especially when high output power is needed. In this case, the electronic power converter comprises typically an intermediate circuit, a converter stage between the generator and the intermediate circuit, and one or more converter stages between the intermediate circuit and one or more energy-storages.
The above-mentioned intermediate circuit is typically a capacitive energy-storage that comprises one or more capacitor modules each comprising one or more capacitor elements and a cooling structure for cooling the one or more capacitor elements. The cooling structure typically comprises one or more heat-sink elements provided with cooling fins for conducting heat to the ambient air and/or with cooling channels for conducting cooling fluid, e.g. water. Each capacitor element comprises an electrode structure for storing electrical energy in the form of electric charge polarization between the electrodes of the electrode structure. The electrode structure is connected to electrical terminals of the capacitor element, and the electrode structure is located inside a casing which can be made of for example aluminum. In many cases, the casing is fitted to an aperture of a heat-sink element.
A cooling arrangement of the kind described above is, however, not free from challenges. One of the challenges is related to a need to arrange a sufficiently good thermal contact between the casing and the heat-sink element. Another challenge is that a significant portion of the heat generation takes place in the electrode structure which carries electrical currents, and therefore the thermal conductivity of the heat transfer path from the electrode structure to the casing can be critical. It is also challenging to connect the electrical terminals of a capacitor element to the cooling structure so as to provide a more direct heat conductive relation between the electrode structure and the cooling structure because the distance between the electrical terminals may vary due to changes in load and/or temperature and/or due to ageing of the capacitor element. Because of changes in the distance between the electrical terminals, a part of the cooling structure connected to one of the electrical terminals should be flexibly supported with respect to another part of the cooling structure connected to the other of the electrical terminals. This, in turn, might be problematic in a shaking environment which is the case in conjunction with e.g. a mobile working machine.